Gilead Sciences Inc. /zigman2/quotes/210293917/composite GILD -0.18% is partnering with Nurix Therapeutics, a biotech working on drugs to destroy disease-causing proteins, the companies announced Wednesday. Under the terms of the multi-year deal, Gilead will have the option to license certain drug candidates from Nurix, and Nurix will have the option to develop up to two programs with Gilead in the U.S., splitting the costs, U.S. sales and losses of those drugs. The deal excludes Nurix's lead drug program, for which Nurix will retain all rights. Nurix will receive an upfront payment of $45 million and is eligible to receive up to approximately $2.3 billion in additional milestone payments and royalties, the companies said. "There are many molecular targets involved in disease pathways that have traditionally been challenging to manipulate using conventional approaches," said John McHutchison, Gilead's chief scientific officer and head of research and development. "Nurix's innovative protein degradation discovery technology provides Gilead with a new strategy to interrogate these drug targets, as we continue to build a pipeline of small molecule therapeutics for patients with cancers and other diseases." Nurix's drug platform targets the ubiquitin system, a natural way the body degrades normal and disease-associated proteins. The company is working on ways to manipulate this system to fight diseases in immuno-oncology and hematology. Shares of Gilead have gained 9% so far this year, while the S&P 500 /zigman2/quotes/210599714/realtime SPX +0.28% has gained 16.4%.